The electron configuration of an element can be abbreviated by using the preceding noble gas. For example, the electron configuration of magnesium is 1s22s22p63s2, but it can be abbreviated as [Ne]3s2, as the electron configuration of neon is 1s22s22p6.

The outer electron configuration is the s'es and p's of the highest principal quantum number. What the **** does that mean? Well, it means the s'es and p's of the highest number in front of the s and p.

Example: 1s2 2s2 2p6 3s2 3p6 is the electronic configuration of Argon. The sum of all the superscripts is 18, which equals the number of electrons which Argon has, which is equal to it's atomic number.

The principal energy levels are numbered starting at 1, and increases by one for each level. The sublevels are named in this order s, p, d, f, g, h, i, etc. (all in alphabetical order after f, but it's a moot point considering h, i, etc. don't even exist, neither naturally nor artificially (yet)).

In order to find the order you must imagine, or draw, arrows coming from the top right to the bottom left going through the last sublevel on each row, and the sublevel below it (on the chart). The order which is found when consulting the chart is 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p, etc.

Atoms are divided into levels of energy. Energy levels are the regions around the nucleus where electrons are likely to be moving. Electrons can move between one level to another, but cannot be in between levels. To move from one level to another, the electron must gain or lose the right amount of energy.

A Quantum is the amount of energy required to move an electron to the next highest energy level. Energy levels grow closer as they move further away from the nucleus.
The number of electrons vary from element to element, obviously. For example, Oxygen (O) has 8 electrons in it. This is determined by subtracting the number of protons(8) from the Atomic mass(16.00).